A conventional preload disk spring assembly includes two pieces of preload disk springs that are positioned face to face and then fitted around a rotary shaft of a rotor to locate between while press against a bear and a retaining ring on the rotary shaft, so as to apply a preload to the bearing to achieve the purpose of preventing the bearing from vibrating and reducing the noise produced by the vibrating bearing.
While the two pieces of preload disk springs for the conventional preload disk spring assembly are positioned face to face, they are not connected together to form an integral body. When being extended through by the rotary shaft to fit around the rotary shaft, the two preload disk springs would inconsistently rotate about the rotary shaft and/or axially vibrate to become biased from their original positions. Further, the conventional preload disk springs are not axially pressed against the bearing, so that the spring force is not evenly acted on the bearing and the preload applied to the bearing is not parallel to the axial direction of the rotary shaft. As a result, the bearing will still vibrate and produce noise.
Moreover, the conventional preload disk spring assembly will interfere with the assembling of the retaining ring to the rotary shaft, so that the retaining ring could not be accurately retained to the rotary shaft to result in undesirable separation of the rotor from a stator assembly.